Methods for use in water purification particularly sewage treatment

ABSTRACT

A method and apparatus for treatment of sewage and waste materials, and while applicable to larger installations, is particularly desirable for relatively small, for example family and multi-family installations, utilizing high rate bio-chemical oxidation/physio-chemical adsorption, in which the sewage is subjected to a primary biological treatment, and a secondary settling treatment, with the primary-secondary effluent, following addition thereto of an organic-inorganic chemical material comprising prereacted floc, a phosphate precipitating material and a nonionic polyelectrolyte, operative to maintain pH and zeta potential favorable to floccuation, being subjected to a tertiary treatment by passage through a mixed filtration and adsorption bed containing activated carbon, the mixed bed being periodically regenerated by a partial wet-gas oxygenation cycle, utilizing a reflex operation in which the products of regeneration are returned to the primary treatment, and in which the final effluent may, for example, contain an average of less than 1 mg/l BOD 5  and an average of less than 0.6 mg/l of suspended solids, an average of less than 0.3 mg/l phosphorus (as PO 4 ), and with a material reduction in sludge. The invention also provides fully automatic cyclic operation and includes a novel tertiary method and structure, including regeneration thereof, as well as the chemical materials utilized and the method of use thereof. In a preferred form of the invention, the chemicals are produced as a dry homogeneous discrete material which may be readily transported and handled in dry form, and formed into an aqueous mix or slurry at time of ultimate use.

This is a division of application Ser. No. 429,488, filed Jan. 2, 1974now U.S. Pat. No. 4,081,365.

BACKGROUND OF THE INVENTION

In the treatment of sewage, particularly involving single-familyinstallations, the so-called "Septic systems" have been employed formany years, which systems employed solely anaerobic action in a suitablecontainer and subsequent discharge of effluent into a suitable groundfield.

More recently, various types of packaged waste treatment plants havebeen developed, which usually employ a modified activatedsludge/extended aeration process, with the final plant effluent normallycontaining approximately 25 ppm BOD₅ and approximately 50 ppm ofsuspended solids, chlorine, for example in tablet form, being utilizedto provide final disinfection.

Systems employing granular-activated carbon are also known, andconsiderable data is at hand as to area and height of beds thereof,flows involved, as well as carbon reactivation requirements. Forexample, see U.S. Pat. No. 3,455,820. The use of carbon columns thusinvolves additional considerations. In addition to other problems as tosize requirements etc., the carbon must be backwashed and eventuallyreactivated or replaced, the carbon usually being removed and heated ina furnace or kiln to a sufficient temperature to oxidize the adsorbedmaterials thereon, but insufficient to oxidize the carbon, for example1500°-1700° F.

In addition, various procedures for "wet oxidative" reactivation ofspent active carbon has also been devised utilizing air and water, thetemperatures involved running from 125° C. to 300° C. or higher and mayinclude relatively high pressures. See, for example, U.S. Pat. No.3,150,105 and No. 3,386,922. It will be noted that operations of thistype normally involve the removal of the carbon from the apparatusinvolved and reactivation in a suitable kiln, autoclave or the like, theoperation normally taking at least a matter of hours. Operations of thistype, requiring removal of the carbon from the apparatus involved, thusnecessitate the use of standby units for operation when a spent unit isbeing reactivated, necessitating a greater number of units than actuallyrequired for the sewage treatment. Consequently, the use of carboncolumns has been limited to installations that make the inclusion of acarbon column and means for reactivating the same both practical andfeasible economically.

More recently the importance of the zeta potential (ZP), a long knownprinciple of physical chemistry, has been recognized in connection withcoagulation, particularly in connection with difficult raw-watercolloids. The zeta potential is a measure of the electro-kinetic charge(in millivolts) that surrounds particulate matter. The charge onraw-water turbidity and suspended matter in domestic sewage is, on theaverage, predominately electro-negative and is strong enough to causesignificant mutual repulsion, so that while coarse fractions, forexample, ranging in particle diameter from 1 mm to 1 micron, may berelatively readily removed by conventional coagulation, fine colloidalfractions, for example, ranging from 1 micron to 10 Angstrom units,cannot. In such case the colloidal size prevents sedimentation and itselectro-negative zeta potential (which may be in the range of -15 to -25mv) prevents agglometaion.

In connection with the study of zeta potential reference is made to thefollowing publications:

Zeta Potential: New Tool For Water Treatment, Thomas M. Riddick,Chemical Engineering, June 26, 1961, July 10, 1961 McGraw-HillPublishing Company, Inc.

Role of the Zeta Potential in Coagulation Involving Hydrous Oxides,Thomas M. Riddick,

Tappi, The Journal of the Technical Association of The Pulp and PaperIndustry, Volume 47, No. 1, January, 1964

Zeta-Meter Helps Filter-Rate Study, D. Lamoureux, Water and PollutionControl (Formerly Canadian Municipal Utilities), August, 1965

As will be apparent from the reference articles, the actual mechanics ofthe zeta potential and reduction in zeta potential of floc is notprecisely factually known at the present time and explanations thusinvolve theoretical concepts. One such concept is described in the firstmentioned article while the second mentioned article refers to thecoating of each colloid with sufficient adsorbed hydrous oxides to bringits zeta potential to zero.

As a result, small systems have involved installations such aspreviously described, with the additional utilization ofbacteria-enzymes etc. in an effort to achieve raid degredation. However,substantially all systems, particularly if the system is intended tobring the ultimate effluent within currently accepted standards, involvea considerable number of individual steps, requiring correspondingnumber of tanks, etc., with none of the systems actually being fullyautomatic, whereby no operating personnel are required. It will beappreciated that this problem is somewhat analagous to the electronicfield wherein almost any electronic problem can be solved if size,number of components, complexity and costs are not of criticalimportance. Likewise, in water purification, almost any degree ofpurification can be achieved if the number of stages, vessels, filters,columns, multiple chemical treatments, size, cost and complexity are notcontrolling factors.

A very interesting and comprehensive study of waste water treatmentconcepts including a review of known types of systems (as of 3-1972)will be found in the treatise "Advanced Waste Water Treatment Concepts"by Dr. James E. Young, P.E.Research Consultant in EnvironmentalEngineering, General Filter Company, Ames, Iowa, appearing in Bul. No.7221, 3-72-2M-W, entitled "GFC Conservation for `better water`",published by General Filter Co.

BRIEF SUMMARY OF THE INVENTION

The invention is directed to a sewage system, particularly forrelatively small installations, for example, one or multiple familyunits, as distinguished from municipal systems and the like, although,apparatus embodying the present invention, readily may be increased asto capacity, for example fifty persons and larger, and if desired, theapparatus may be utilized in multiples. The method and apparatus of theinvention is readily adapted to automatic cyclic operation wherebyconstant maintenance or monitoring of the operation is eliminated, withonly periodic replenishment of chemicals employed therewith beinginvolved.

The system utilizes a combination primary-secondary treatment includingphosphate removal, involving zeta potential control by destabilizationand flocculation, as well as pH control, followed by a tertiarytreatment having an upflow mixed media mineral filtration bed andassociated activated carbon adsorption bed, with reactivation of thecarbon being achieved in a novel reflex, wet-oxidation operation whichtakes place in-situ, and the reactivation products returned to theprimary and secondary treatment. As a result of such reflex action, ahigh degree of efficiency is achieved in the oxidation procedures, andsludge deposits in the primary-secondary operations are also materiallyreduced, whereby the system may be operated over relatively long periodsof time without excessive sludge accumulation in the primary-secondarysystem, whereby cleaning operations may be required only atexceptionally long intervals.

The system herein described and illustrated may be readily cyclicallyoperated, employing, for example, a 24-hour cycle, in which aeration inthe primary-secondary unit takes place over a period of maximum use ofthe system, for example from early morning hours to late evening hours,followed by a period of settling during the after-midnight hours, and arelatively brief period during a "pump-down" cycle, i.e. during whicheffluent is pumped through the tertiary unit. Regeneration of thetertiary unit may take place automatically, for example during theaeration cycle, particularly near the end of the latter. Theregeneration cycle involves the use of water, advantageously renovatedwater received from the previous pump-down cycle and preferably heatedto a suitable temperature, for example 160° F., which is passed throughthe tertiary unit, in the same direction as flow during the pump-downcycle, air under pressure being similarly admitted to the tertiary unit,preferably initially only air, followed by a combined air and water flowand terminated with a flushing operation employing only water. Thepurged water and contents discharged from the tertiary unit are returnedto the primary-secondary unit.

The invention employs both inorganic and organic chemicals for phosphateremoval, flocculation and agglomeration of suspended and colloidalmaterials, control of zeta potential and control of pH, which areintroduced into the system as an aqueous mix or slurry, the materialpreferably being initially produced as a homogeneous discrete drymaterial which may be readily handled and transported, and mixed withwater prior to its use in the system.

It will be appreciated that the character of sewage to be treated mayvary widely, both as to inorganic and organic content, and thus also asto its pH value, and the chemical material here involved may be, ineffect, "tailor-made" to average conditions associated with the sewageor wastes to be treated. By suitable selection and amounts of thechemical constituents, favorable pH values may be maintained in thesystem along with effective zeta potential control, wherebysubstantially instant flocculation and very rapid agglomeration ofsuspended and colloidal materials results.

While a number of inorganic materials may be employed, depending uponthe specific application, comprising those commonly employed in waterand sewage treatment, i.e. aluminum and iron sulphates, sodium aluminateand ferric chloride, as hereinafter discussed in detail, is believedthat in most applications aluminum sulphate and/or sodium aluminate willbe preferable from the standpoint of cost, efficiency in use, absence ofcolor and taste problems, etc. Such combinations with aluminum saltsprovide a substantially universal material capable of use with thepresent invention in substantially any application, and in view of theadvantages of such material, it is believed that the other materials maynormally be relegated to usage only when their specific characteristicswould, in specific applications, offer some advantage over the use ofthe preferred materials.

In general, the chemical material will comprise an inorganicagglomeration-promoting material, preferably an organic non-ionic highmolecular weight polyelectrolyte, an inorganic material for effectingphosphate removal if such removal is included, and a material forproviding a floc for colloidal and suspended material agglomeration. Thefloc-producing material and that employed in phosphate removal may bethe same or different materials. Thus, assuming that aluminum sulphateor sodium aluminate are employed as such materials, selection willnormally be determined by the character of the sewage to be treated.Likewise, where aluminum or other sulphate is employed as theflocculent, an inorganic material reactive therewith, such as soda ash,i.e. sodium carbonate, or operational equivalent is included whereby thedesired amount of floc will be produced.

The various chemicals, contrary to prior teaching, may be mixed togetherand supplied as a liquid or suspension of prereacted floc. Where thesewage involved has an average pH relatively close to 7, and includesphosphates which are to be removed, normally aluminum sulphate may beemployed for the phosphate removal, with the pH of the effluent beingmaintained close to 7 and control of zeta potential effected bydestabilization. On the other hand, if the sewage or waste has anaverage pH that is relatively low, i.e. acidic, it may be preferable toemploy sodium aluminate for phosphate removal, with the latter thushaving a greater effect on the pH, again bringing it up close to 7, i.e.6.8 to 7.1. Intermediate control may be achieved by a mixture of bothsalts in suitable proportions.

Preferably the chemical mixture is supplied in two different steps, partto the tertiary unit with the effluent from the primary-secondary unit,by injection in measured amounts into the supply line from theprimary-secondary unit to the tertiary unit, and part supplied directlyto the primary-secondary unit, for example just prior to the settlingcycle. The invention enables, for example, the production of a compact,highly efficient aerobic sewage and waste system that replaces theseptic tank, for example, having a 500 gal. per day capacity (adequatefor at least six persons), with the achievement of organic reduction inexcess of 99%, as compared with the 25% to 40% reduction of thetraditional septic tank system, and results in the production ofreusable water of high purity, i.e. removal of 99% of all solids, odorand tastes in the effluent as well as a material reduction inphosphates.

The system readily may be fully automatic, requiring no controllingpersonnel, and can be installed in any terrain, as the system requiresno adsorption field tile bed. The effluent may be discharged into astream, used for irrigation, recirculated for use in air conditioningsystems and waste plumbing fixtures, etc. where permitted. By simplechlorinating and possibly reverse-osmosis procedures it even may beemployed as potable water.

In addition, wastes are treated over 75% faster than standardmicro-biological systems. It facilitates the rapid assimilation ofoxygen by the wastes and accelerates the bio-chemical oxidation rate.The exclusive "once through" process involved eliminates the need forsettling ponds and extensive sludge removal as well as numerous tanks,etc. and multifold operations. In applications where disinfection isdesired or required, automatic chlorination and/or reverse-osmosissystems may be readily included.

Another feature of the invention is the provision of a novel tertiaryfiltration and adsorption structure and methods of operation, andregeneration thereof utilizing a wet-air oxidation.

A further feature of the invention is the production of a singlechemical material in the practice of the invention which may be producedin dry or liquid form, and will provide pre-reacted floc, material forphosphate removal and a non-ionic polyelectrolyte for agglomerationpromotion.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein like reference characters indicate like orcorresponding parts:

FIG. 1 is a semi-schematic flow diagram of a system employing thepresent invention;

FIG. 2 is an isometric view, with portions broken away and transposed,of apparatus constructed in accordance with the present invention;

FIG. 3 is a sectional view of the apparatus illustrated in FIG. 2 takenapproximately on the line III--III of FIG. 4;

FIG. 4 is a plan view of the apparatus illustrated in FIG. 2, withportions broken away to simplify the disclosure;

FIG. 5 is a sectional view of the apparatus, taken approximately on lineV--V of FIG. 3;

FIG. 6 is a sectional view taken approximately on the line VI--VI ofFIG. 4, with portions broken away to show details of construction;

FIG. 7 is a sectional view taken approximately on the line VII--VII ofFIG. 4;

FIG. 8 is a sectional view through one of the jet structures illustratedin FIGS. 2 and 3;

FIG. 9 is a sectional view, similar to FIG. 8, of a modified jetstructure;

FIG. 10 is a time diagram illustrating the examplary sequence ofoperations over 24-hour period; and

FIG. 11 is a chart illustrating the relationship of the chemicalsinvolved with respect to pH.

GENERAL PROCEDURES

FIG. 1 illustrates a semi-schematic flow diagram depicting the generalarrangement and operations employed, in which the reference numeral 1indicates generally a primary-secondary treatment unit or stage, thereference numeral 2 a tertiary treatment unit or stage, and thereference numeral 3 a storage reservoir, for renovated water. The rawsewage enters the primary-secondary treatment stage through a supplyline 4, connected to the sewage source by a line 5, preferably throughan intermediate holding tank 6 with the supply to the primary-secondarytreatment being controlled by a valve VI, for example, a power-actuatedvalve disposed in the line 4. The primary-secondary stage 1 isoperatively connected with the tertiary stage 2 over a pump P1 and line7, which may have a flow controlling valve FV1 and a check valve CV1interposted therein, with effluent discharged from the tertiaryapparatus being conducted over a line 8, which may have a flowcontrolling valve FV2 and a power-actuated control valve V2 disposedtherein, to the storage reservoir 3.

Thus the sewage may be controlled in the primary-secondary treatmentstage, discharge therefrom being prevented by the de-energized pump P1,and processed, for example subjected to suitable aeration, followed by aperiod of settling, during which the valve V1 may be closed, whereby anyincoming sewage during such period may be accumulated and retained inthe holding tank 6 during the settling period, so that such settling isnot disturbed.

Following settling, a pump-down phase may be initiated in which pump P1is actuated to effect pumping of the effluent in the primary-secondarystage apparatus to the tertiary treatment stage 2, with the outputtherefrom flowing through line 8, and open power-actuated line valve V2therein, at a suitable rate, as determined, for example, by either orboth flow control valves FV1 and FV2, into the reservoir 3, accumulatinga predetermined volume of liquid therein, with excess liquid beingdischarged through the line 9.

As hereinafter described in detail, suitable chemical materials may besimultaneously supplied by pump P2 from a chemical supply CS, throughlines 10 and 10a, to the line 7, for example between check valve CV1 andflow valve FV1, and thus act upon effluent from the primary-secondarytreatment stage as it flows through line 7 into the tertiary treatmentstage. At a selected period or periods, chemicals may also be dischargedinto the primary-secondary stage by means of a similar pump P3, throughcommon line 10 and line 10b.

At predetermined periods following the pump-down phase the tertiarytreatment apparatus may be purged or reactivated by means of awet-oxidation process, employing for example air and water. Such processmay be readily effected by the use of renovated water from the reservoir3, preferably heated to a desired temperature, which is pumped, by meansof a submerged pump P4, through line 11, flow-controlling valve FV3,check valve CV2 and line 7 into the tertiary treatment stage, with checkvalve CV1 preventing reverse flow into the primary-secondary treatmentstage during such operation. Discharge of such water from the tertiarytreatment stage takes place through a line 12, under the control of apower-actuated valve V3 with the line 12 discharging its contents intothe primary-secondary treatment apparatus. Air under pressure may besupplied from an air compressor C1, through a line 13, having a checkvalve CV3 therein, to the tertiary treatment apparatus, in conjunctionwith the admission of water through the line 11, to provide a wet-airregeneration of such apparatus, as hereinafter described in detail. Asillustrated, power-actuated valves V2, V3 may be by-passed by manualvalves V2', and V3' for manual operation, if necessary or desired.

As subsequently discussed in detail, the system generally described inparticularly adaptable for use in comparatively small installations asfor example home or multiple home installations in which the variousphases of operation referred to may take place cyclically over a 24-hourperiod, for example collecting sewage in the primary-secondary treatmentstage over a period from early morning hours, for example around 5 A.M.to the midmight hours, for example around 1 A.M., during which periodthe contents therein are continuously aerated. At or preferably near theend of the aerating period, conduction of raw sewage to theprimary-secondary stage may be discontinued and the tertiary treatmentstage 2 regenerated by the wet-oxidation process described, utilizingair from compressor C1 over the line 13, and water from the reservoir 3over line 11, with the discharge from the stage 2 being returned, overline 12, to the primary and secondary stage.

Following the end of the aeration period, a settling period may beeffected, with any incoming sewage being collected in the tank 6, at theend of which settling period the output from the primary-secondary stage1 is pumped into and through the tertiary stage 2, with the outputthereof being accumulated in the reservoir 3 and any excess waterdischarged over the line 9, concluding a complete cycle of operationwhich may be immediately followed by a second collection and aerationcycle.

The chemical injected by the pumps P2-P3, comprising, for example, amixture of prereacted floc produced from a flocculating agent, and ifnecessary a reactive agent therefor, a phosphate reactive material, andan agglomeration-promotion agent, operative to reduce the zeta potentialto -5 to +5 ZP, produce a relatively instant floc-agglomeration, i.e.,in a matter of seconds, while maintaining the pH of the effluent at avalue favorable to flocculation and agglomeration, and provide colloiddestabilization.

Contrary to previous, accepted teachings, favorable results are achievedwith use in the apparatus, of the chemical components in the form of amixture and while equivalent materials may be employed in accordancewith established techniques in the field, preferably, as previouslymentioned, there is employed for the chemical material a suitablemixture of aluminum sulfate (alum) and sodium carbonate (soda ash),sodium aluminate (or mixtures thereof) and a non-ionic polyelectrolyte,preferably a polyacrylamide.

The practice of the invention enables the achievement of exceptionalhighly efficient results with a bare minimum number of operative stepsand a minimum amount of tanks and other equipment, at the same timeenabling the achievement of a substantially completely automaticcontinuous operation of the system, requiring primarily only materialsupply maintenance at suitable intervals, for example monthly orsemi-monthly, for replenishment of the chemical materials utilized.

To facilitate explanation of the invention, the apparatus initially willbe described, followed by a description of the overall operation andfinally details of the materials involved, background theory and theexceptional results obtained detailed.

THE APPARATUS

FIGS. 2 through 7 illustrate a preferred embodiment of the invention,providing a complete sewage system as a unitary structure, which may bereadily fabricated of sheet steel (as illustrated) reinforced concrete,etc., assembled and transported to the locality of use.

In general, the device employs a single unitary tank or housingstructure designated generally by the reference numeral 14, which asillustrated in FIGS. 2 and 3 is rectangular in configuration andgenerally L-shaped in longitudinal cross-section, having a bottom wall15, end walls 16a, 16b, side walls 16c, 16d, a top wall 17 adjacent theend wall 16a and an upper end wall 18 extending upwardly from the topwall 17. The end wall 16c and adjacent portions of the side walls 16band 16d are extended upwardly to the top edge of the upper wall 18,forming a vertically extending column 14', the top edge portions ofwhich defining an access opening 19 which may be closed by a suitablecover or grill (not illustrated). A partition wall 20 extendstransversely across the tank 14 between side walls 16b and 16d, with thewalls 16a, 16b, 16d and 20, together with the top wall 17, defining aprimary-secondary chamber 21. The partition wall 20, end wall 16c andside walls 16b and 16d define a second chamber 22, in which is disposedthe tertiary treatment apparatus 2 and the renovated water reservoir 3.

In the embodiment illustrated, the tertiary unit 2 and reservoir 3 areof generally rectangular configuration, the tertiary unit 2 beingsupported from the bottom wall 15 while the reservoir 3 is supported ona suitable platform 23.

The unit is completely self-contained, requiring no additional tanks,ground fields, or the like and consequently may be installed eitherabove or below ground, and in or on any terrain or structure capable ofadequately supporting the same.

After placing in normal operation, it is completely automatic inoperation, requiring (other than sewage connection, etc.) onlyelectrical connection and periodic maintenance with respect to chemicalreplenishment.

PRIMARY-SECONDARY TREATMENT STRUCTURE

Details of the primary-secondary apparatus are illustrated in FIGS. 2, 3and 5 and the basic structure, tank 14 and tank 6 each may be ofgenerally conventional sheet metal construction.

Disposed adjacent the bottom of the primary-secondary chamber 21 is asuitable aerating unit 24, with air being supplied thereto by an airsupply line 25, running from the unit 24 to a blower B having a suitableair inlet line 26 which, for example, may run to an air inlet on asuitable control box (not illustrated). The aerating unit 24 may be ofcommercial design, readilyprocurable on the open market, and is adaptedto discharge air received from the line 25 throughout the bottom area ofthe chamber, with such air thus rising through the contents therein tothe top surface thereof.

The contents of the chamber 21 are adapted to be withdrawn therefrom bymeans of the submersed discharge pump P1 which is illustrated as beingoperatively connected by line 27, the check valve CV1 and a strainer Sto the flow control valve FV1 and line 7. It will be apparent that uponoperation of the pump P1 effluent will be discharged through the line 7until the liquid level in the chamber drops approximately to the levelof the intake openings of the pump P1 as determined by a suitable floatswitch 28, having an actuating float 29, the switch and float structurebeing of known construction, commercially procurable. Check valve CV1prevents a reverse flow.

The holding tank 6 is constructed of suitable size commensurate with theoperational capacity of the apparatus and is adapted to receive rawsewage, in the embodiment illustrated, from the supply line 5. Thepower-actuated valve V1, disposed in the discharge line 4, may be ofelectro-mechanical type and is so positioned, for example in the column14', that it may be readily serviced or replaced, if necessary, withoutdismantling any other portion of the system. The holding tank 6, may beof closed construction, in which case it may be provided with anoverflow or vent pipe 30, the latter being laterally displaced withrespect to the line 4 as will be apparent from a reference to FIGS. 2, 4and 5.

Also, as illustrated in FIG. 2, the line 12 from the tertiary treatmentapparatus 2 extends laterally into the column 14' and then downwardlywith its open end disposed to discharge into the chamber 21.

The supply container CS, is operatively connected to suitable feed pumpsP2 and P3, the inlet sides of which are connected over line 10 to theoutlet of the container CS, illustrated as being mounted in the column14' above the chamber 21. Any suitable means may be associated with thetank CS or with pumps P2 and P3 to insure feeding of predeterminedamounts of chemicals into the line 7 over line 10a, and into the chamber21, over line 10b or the pumps P2, P3 may be suitable constructed tofeed predetermined amounts. Suitable means may be provided for effectiveagitaion of the chemical material in the tank CS, for example anelectric agitator employing an electric motor CS1 which rotates suitableagitator blades CS2, as illustrated in FIGS. 2, 3 and 5, therebyinsuring a uniform feed.

The chamber 21 may be provided with an overflow pipe 21' having aflap-type check valve CV4 therein preventing a back flow. The line 7 maybe provided with a by-pass line 7' communicating with the overflow line21' whereby, if desired for any reason, effluent in theprimary-secondary chamber may be pummped out the overflow line. Flowthrough the line 7' may be controlled by a manual valve V4.

TERTIARY TREATMENT APPARATUS

Details of the tertiary treatment stage or unit 2 are illustrated inFIGS. 2 and 3. The tertiary treatment unit comprises a generallyrectangularly shaped housing or container, indicated generally by thisreference numeral 31, having a tubular intermediate member 32, a topmember 33 and a bottom member 34. Extending across the interior of theupper portion of the intermediate member 32 is a grid member, indicatedgenerally by the numeral 35, which in the embodiment illustrated may beof cast construction and secured to and supported by a plurality ofperipheral blocks 36, welded or otherwise secured to the side walls ofthe member 32.

Also disposed in the upper portion of the member 32, adjacent the topmember 33, is a water collection structure in the form of a troughmember 37, illustrated as being of inverted generally triangularconfiguration in transverse cross-section, having a lower imperforatesection 38, an upper perforate section 38' and respective end walls 39,with the perforate side wall portions 40 forming the liquid inlet of thestructure. The perforate section, which may comprise a suitable screenor the like, is provided with openings of a size to provide adequateliquid flow through the screen but prevent the passage of particles ofpredetermined size into the trough. The latter is also provided with apressure release port 41 therein which extends to the exterior of thestructure and is closed by a pressure relief valve 42, operativelycommunicating over a line 42' with the line 8 to the reservoir 3. Thetertiary unit is also provided with a pressure gauge 43 and an airventing valve 44, both of which are mounted on the top 33 incommunication with the housing interior. As illustrated, the lines 8 and12 are connected by a T-connection with the common line 45 extendinginto the trough member 37, whereby liquid entering the lines 8 or 12, asdetermined by the operating positions of the valves V2 and V3 is takenfrom substantially the extreme top of the housing 31. The trough member37 may be supported, for example, in addition to the support provided bythe outlets 41 and 45, by a plurality of blocks 36' rigidly mounted onthe adjacent side walls of the member 32.

As illustrated in FIGS. 2 and 3, extending across the housing 31adjacent the bottom 34 thereof is a partition wall 46, forming a chamber47 at the bottom of the structure. As illustrated in such figures, aswell as in FIG. 7, the lines 7 and 11 are connected to a common inletpipe 48 for discharging liquid in either of the lines 7 or 11 into thechamber 47. A baffle member or plate 49, suitably supported by legs orthe like from the bottom 34, extends above and across the inlet opening48' of the pipe 48, thus preventing direct discharge of liquid againstthe partition wall 46 and effectively distributing flow throughout thechamber.

The wall 46 is provided with a plurality of jets, indicated generally bythe numeral 50, a preferred embodiment of which is illustrated in FIG.8.

In this construction the jet comprises an externally threaded shankmember 51 adapted to be threaded into the supporting wall or plate 46and secured in operating position by a lock nut 52 threaded on the shank51. Disposed at the opposite face of the wall 46 and encircling theadjacent end of the shank 51 is a disk member 53 formed, for example,from sheet metal and provided with a downwardly extending peripheralflange 54. Formed in the flange are a plurality of notches 55, theconstruction illustrated employing six such notches, which open on thefree-peripheral edge of the flange, with the intermediate portions ofthe latter seated on the adjacent face of the wall 46. The latter thuscooperates with the notches in the flange to define openings adapted todischarge liquid on and along the adjacent face of the wall 46. Asillustrated, the shank is of hollow construction having a bore 56therein, with the side walls of the shank adjacent the member 53 havingone or more ports or openings 57 therein whereby liquid may flow fromthe interior of the shank outwardly into the chamber, defined by themember 53 and the wall 46, with such liquid thus being dischargedthrough the slots 55. If desired the bottom end of the shank 51 may beprovided with similar openings 57' for the ingress of liquid and/or airinto the jet structure, and as illustrated may be beveled at its lowerend.

The modified jet structure illustrated in FIG. 9, comprises a hollow ortubular shank 51, likewise provided with screw threads on its exteriorface, with such shank extending through cooperable opening 46' in theplate 46 and engaged with mating threads formed on the side wallsdefining the opening and locked in position by lock nut 52. The upperend of each jet is provided with an enlarged integrally formed head 53',which, for example, may have a hexagonal or octagonal peripheralconfiguration, that illustrated being provided with six side walls 54'.The head 53' is provided with a plurality of radially extending bores57" which communicate at their inner ends in the bore 56 of the shank51' and at their outer ends open on a respective wall 54', whereby inthe example illustrated, six such bores are provided. The head 53' isalso provided with a like number of bores 58, the axes of which extendsubstantially parallel of the shank 51' with the upper ends of each ofsuch bores intersecting an associated bore 57", and the lower ends ofeach of such bores opening on the annular shaped bottom wall 59 of thehead.

Disposed in the intermediate portion of the tertiary unit and extending,for example, from the wall 46 to somewhat above the grid 35 is aplurality of layers, L1-L5, of filtering and adsorption materials. Inthe specific embodiment illustrated, there are provided a plurality oflayers L1-L4 of mineral, for example red flint, the layers being gradedin size with the largest at the bottom and the smallest at the top,which layers form a filtration bed, on the top of which is disposed anadsorption layer L5 comprising a hydraulic mix of activated carbon andquartz, details of which will be subsequently discussed under the head"Operating Parameters".

STORAGE SYSTEM FOR RENOVATING WATER

FIGS. 3 and 6 also illustrate schematically details of the storagesystem for the renovated water to be utilized in the regeneration of thesystem.

As illustrated, the reservoir 3 comprises a generally rectangular tank61 disposed to receive the effluent from the tertiary treatment unit 2over the supply line 8, excess effluent, following filling of the tank61 to a desired level, being discharged through the outlet line 9communicating with the tank. The line 11 for conducting renovated waterfrom the tank 61 to the chamber 47 of tertiary unit is operativelyconnected with the discharge side of the submersed pump P4 in the tank61, the inlet of which pump opens on the tank interior. The pump P4 mayinclude a self-contained float switch, or the like, for deenergizing thepump when the liquid level in the tank drops to a predetermined level.

The tank 61 is also provided with an electrical heating unit, indicatedgenerally by the reference numeral 62, (FIG. 6) through which renovatedwater in the tank is adapted to be circulated by means of a suitablepump P5 having its inlet opening communicating with the lower portion ofthe tank and its discharge opening connected by a line 63 to heatingunit 62 with the renovated water, following passage through the heatingunit being discharged through the outlet pipe 64 thereof. Thus byactuation of the heating element 62 and operation of the pump P5 therenovated water in the tank 61 may be brought up to a suitabletemperature, for use in connection with the reactivation or regenerationof the material of the tertiary treatment system.

TERTIARY REGENERATION

In the embodiment of the invention illustrated, the tertiary structure 2is adapted to have the filter and adsoprtion beds L1-L5 thereofperdiocally regenerated, for example between each pump down cycle fromthe primary-secondary structure. Such regneration is effected by the useof a regenerating gas, for example air under pressure, and water, withthe latter preferably being suitably heated. Where air is employed, suchair may be supplied from a compressor C1, having suitable capacity as tovoluem of air and pressure, while the water, employed at least in partas a flushing medium preferably makes use of renovated water which isaccumulated, preferably heated, and stored, until time of use, in thereservoir 3.

As previously described with respect to the tertiary unit, the air line13 from the compressor C1 is operatively connected with the inlet 48 ofthe tertiary unit over a check valve CV3, which permits passage of airthrough the line 13 but prevents a reverse flow of water therein whenair is not being supplied to the unit. Likewise, the water from the tank61 is supplied to the tertiary inlet over line 11 and check valve CV2,with the rate of flow through the line 11 being determined by thesetting of the manual flow-control valve FV5. As hereinafter discussedin detail under the heading "Operating Parameters", while the flow ofair and water through the tertiary unit may be variously selected,excellent results have been obtained when only air in suitable volumeand under suitable pressure is initially passed through the tertiaryunit for a predetermined period, followed by a combined flow of air andwater therethrough, and finally by a flush with water only.

In general, the volume, pressure and duration of the air flow during theinitial flow of only air should be such that the beds of the tertiaryunit will be expanded sufficiently to insure satisfactory exposure ofall particles of the beds to the regenerative satisfactory exposure ofall particles of the beds to the regenerative action of the air andwater, but insufficient to materially effect the layer distribution ofsuch particles. It will also be noted that a chamber is provided abovethe beds, i.e. between the top of the adsorption bed and top 33, formignwhat might be termed a "regeneration chamber" in which the material isrenewed by subjection to the oxidizing action of the air and water.

After passing through the tertiary unit materials with entrained purgingair and water is returned to the primary-secondary chamber 21 over valveV3 and line 12. It will be appreciated that the regenerating operationmust fully remove all material accumulated in the tertiary unit, as aresult of the filtration and adsorption processes, with sufficientflushing water being employed to insure that the effluent at thedischarge side of the tertiary unit, after regeneration, is of the samequality as the normal output effluent from the system, i.e. that allimpurities are effectively removed from the tertiary unit duringregenerating process. If this were not the case, the regenerating cyclebeing insufficient to fully purge the system, a build-up would takeplace in the tertiary unit necessitating periodic shut-down and cleaningor replacing of the materials.

In review, the regenerating water flow thus takes place during operationof the pump P4, with the flow of water being controlled by the flowvalve FV5, the water passing over line 11 and check valve CV2 into thetertiary unit and discharged therefrom over line 12 and valve V3 to theprimary-secondary unit.

It will thus be appreciated that the regeneration cycle is, in effect, areflex operation in which the purged materials are recycled and thusfurther reacted upon biologically in the primary-secondary treatment.

CYCLIC OPERATION OF THE SYSTEM

As previously described, the system may be operated in cyclic manner,for example, in repetitious cycles of 24 hours each with the operationsbeing coordinated with the normal use of the system.

A typical, and believed preferably cycle of operation for use with thesystem illustrated is diagrammatically presented in FIG. 10. In thisfigure the cycle is graphically illustrated, for convenience as astraight line chart, vertically orientated but it will be appreciatedthat it would be more accurately depicted as a closed circle with thetop and bottom lines, representing 12:00 A.M., superimposed.

Referring to the chart, it will be noted that from approximately 5:40A.M. to the following 2 A.M., a period of 20 hours, 20 minutes, aerationtakes place in the primary-secondary chamber 21, during which timeapproximately 500 gallons of incoming sewage may be received into thechamber over the line 4, valve VI in such line being open to permit suchoperation. Valves V2 and V3 are motorized units and preferably are wiredfor simultaneous operation with ports being reversed, i.e. V2 open whenV3 closed and vice versa. Consequently, the valves will be set from thelast pump-down cycle, i.e. V2 open and V3 closed. During this operation,pump P1 is inoperable so that no effluent will flow from theprimary-secondary chamber to the tertiary unit 2, although valve V2 isopen and valve V3 closed. From approximately 5:40 A.M. to 1:00 A.M., theheater 62 will be energized and the circulating pump P5 actuated (itbeing assumed that an intermediate cycle of operation is involved inwhich the reservoir 3 has been filled with renovated water during thepreceding cycle.)

Thus referring to the diagram, at 5:40 A.M. incoming sewage maydischarge through valve V1 and line 4 into the primary-secondary chamber21, and simultaneously therewith blower B will be actuated to supplyaeration in such chamber, heating unit 62 will be energized andcirculating pump P5 actuated to effect a circulation and heating ofwater in the tank 61.

At the following 12:00 A.M. feeding of chemicals to theprimary-secondary chamber 21 may take place over pump P3 and lines 10and 10b, such chemical feeding taking place in the example illustratedfor a period of approximately five minutes, i.e. to 12:05 A.M.

Heating of the renovated water in the reservoir 3 continues to takeplace until 1:00 A.M. At this point valve V3 is opened, valve V2 closed,and compressor C1 actuated whereby air will flow in line 13, throughcheck valve CV3 and discharge ring 60 into the chamber 47, with such airflow being at a suitable volume, suitable pressure and for suitableduration, as hereinafter discussed under the heading "OperatingParameters". Such air will tend to lift or expand the filtration andadsorbent beds in the tertiary unit, with excessive movement of the bedmaterials being prevented by the grid 35. However, the air willsufficiently expand the beds as to insure a permeation of air andsubsequent water flow throughout the bed structure, resulting in aregenerating, oxidizing action of all materials accumulated therein. Atthe end of the initial air regeneration phase the pump P4 will beactuated, operative to pump the heated water through line 11, flow valveFV5 and check valve CV2 into the chamber 47 of the tertiary unit, upthrough the filtration and adsorption beds along with the continued airflow, and discharged through the valve V3 and line 12 into theprimary-secondary chamber. The combined air-water flow will continue fora predetermined period, followed by predetermined period of only waterflow, sufficient to insure a complete flushing of the tertiary unit atthe end of the regeneration period will be of equal quality with thenormal output effluent from the system. In the example illustrated inFIG. 10, the regeneration period, illustrated in exaggerated form, maybe approximately 20 minutes, with the air and water discharged from thetertiary unit likewise being returned over the valve V3 and line 12 tothe primary-secondary unit. At the end of the regeneration cycle, i.e.approximately 1:25, pump P4 is deactuated, for example by an internalfloat-switch incorporated therewith.

Aeration continues to take place, in the example illustrated, until 2:00A.M. until which time the blower B is deactuated and valve V1 closed.Any incoming sewage thereafter is retained in holding tank 6 while asecondary settling period takes place in the chamber 21. This continues,in the example illustrated, for a period of 3 hours until 5:00 A.M. atwhich time valve V2 is opened, valve V3 closed and pump P1 in thechamber 21 actuated, thereby pumping effluent in the chamber 21 throughline 7, check valve CV1 and flow control valve FV1 into the tertiaryunit, with the effluent from the latter being discharged through line 8and open valve V2 into the tank 61 for renovated water. When the waterin the latter reaches its original level any excess thereover will bedischarged through the line 9 and may be utilized for any suitablepurpose, or collected in a suitable holding tank for subsequent use.Simultaneously, with the actuation of the pump P1, the pump P2 isactuated to feed chemicals through lines 10 and 10a to line 7 so thatadditional chemicals are supplied to the effluent being conducted to thetertiary unit. In this case, the feed of chemicals into the line 7 willbe proportionate to the effluent flow so that the pump P2 will beactuated throughout the period of actuation of the pump P1.

At the end of the pump-down phase the valve V1 will be opened,permitting discharge of any accumulated sewage in the tank 6 to enterthe primary-secondary chamber 21 and any subsequent sewage flow to passdirectly into such chamber. Likewise, the heating unit 62 in tank 61will be energized and circulating pump P5 actuated to begin therenovated water heating phase. Simultaneously with the latter, theblower B will be actuated, thereby again initiating aeration in theprimary-secondary chamber 21, with aerobic-chemical oxidation continuingfor the remainder of such new phase, i.e. until the next settling phase.The apparatus thus starts the repetition of another 24-hour cycle ofoperation.

It will be appreciated that the operation may be continuously automaticrequiring no manual attention whatsoever, the only maintenance beingrequired being that of periodically replenishing the supply of chemicalsin the tank CS. The chemical materials may be so produced that the tankCS will be adequate for at least between 30 and 60 days operation of thesystem, so that suitable maintenance programs may be readily supplied tothe purchaser of such a unit.

CHEMICAL TREATMENT

The general method employed and apparatus utilized in the practicethereof, together with the mechanical operation of such apparatus hasbeen previously discussed. The chemicals and chemical treatment employedin the practice of the invention will now be described.

However, before discussing such chemical treatment, it is believeddesirable to briefly review the chemical materials, procedures andconcepts involved in known treatments of raw water and sewage.

The use of coagulants in water purification has been a standardprocedure for many years, the reaction with the coagulant to produce thedesired floc in the purification of raw water often, where feasible,making use of the natural alkalinity of the water to produce the desiredfloc. The desirability of control of pH has been recognized over theyears and where necessary additional acidic or alkaline materials havebeen added in an effort to effect a control of pH to the value mostsuitable for flocculation.

However, in the past, the teaching with respect to sewage treatment andthe use of coagulants has quite consistently been that the coagulant andalkali should not be premixed but should be added in separate stages toavoid the addition of prereacted floc to the sewage, and it has beenstated that in such case both colloid and color removal will besubstantially nil. It, therefore, has been deemed essential toseparately introduce the coagulant and alkali in separate vesselswhereby the actual formation of floc would take place in the main bodyof water.

More recently, the importance of zeta potential also has been recognizedand in particular, the necessity of having the zeta potential in thevicinity of zero, particularly -5 to +5 if optimum flocculation is to beachieved.

In recent years with the high use of detergents and the like containingphosphates, the problem of phosphate removal has also increased inimportance, and adequate reduction of the phosphate content in sewagewater must also be taken into consideration.

Likewise, polyelectrolyte coagulant aids have more recently beenemployed in connection with water clarification processes and ingenerally, involve electrolytic activity although the terms as currentlyused includes naturally occurring organic flocculants, many of whichfunction solely through hydration. Polyelectrolytes may be classified asanionic, cationic or non-ionic in dependence upon the charges appearingin solution, non-ionic having both positive and negative chargespresent. At the present time the mechanisms of such aids are notcompletely understood and are currently undergoing extensive research.It would appear that the most dependable tool in studying anddetermining coagulation processes and efficiency is still the well-knownjar test, which might be deemed "trial and error" tests, i.e., empiricalstudies as distinguished from theoretical or calculated studies.

While the overall results of the present invention involve a combinationof steps, purely physical, as well as biological-chemical treatment,etc., the success of the invention is also the result of what may bedeemed and is believed to be a major breakthrough in water purificationprocesses with respect to the physio-chemical concepts involved and theability to provide a single chemical material having all necessarychemicals in proper proportion to achieve the desired results. Theinvention thus enables the practice of an extremely simple chemicaltreatment to complement the extremely simply physical processesemployed, utilizing correspondingly relatively extremely simple physicalstructures, which for example, may employ merely two stages, i.e., twovessels, one involving the primary and secondary treatment and the otherthe tertiary treatment as distinguished from the customary practice ofemploying a relatively large number of vessels each having a respectivefunction and usually involving its own operational and chemical steps.The ability to employ a single chemical material also contributes to theobjective of producing a completely automatic system requiring nomonitoring thereof and thus no attendant personnel.

The present invention also demonstrates the complete feasibility ofintroducing prereacted floc to sewage, i.e., the resultant of an aqueousmixture of suitable coagulant and alkaline material reacting therewith,or the equivalent thereof, to produce the desired floc, with thematerial of the present invention also including, if desirable, materialfor phosphate removal, and an agglomeration-promoting material such as asuitable polyelectrolyte.

The material of the present invention thus involves, at time of use, anaqueous mixture of a plurality of functional materials, i.e., acoagulant and an alkaline material reactive therewith to produce a floc,or its equivalent, an agglomeration-promoting material, and a phosphateprecipitating material, with the floc thus being, in effect, prereactedin the mixture prior to introduction into the receiving effluent.

It will be appreciated that the specific proportions of the variousmaterials will, of necessity, depend upon the character of the sewagebeing treated, and the broad range of amounts of the respectivematerials must be generally established in terms of their functions inthe sewage in which they are introduced. It is believed apparent that insubstantially any system, the amounts of phosphates, suspended solidsand colloidal material as well as the pH range, will tend to approachnormal or average values for the specific system, as well as relativelyreadily ascertainable peak levels, from which figures the necessaryquantities of the most suitable chemical materials may be relativelyeasily initially estimated or computed, following which physical testsmay be run to provide a final check out of the selected proportions andinsure optimum results.

Likewise it will be appreciated that as the material involves an aqueousmixture, the amounts of the various components may be simply resolved interms of amounts per liter of effluent to be treated.

It will also be apparent that while, in many instances, it may bepreferable to employ the same material for both phosphate removal andthe formation of floc, another suitable material could be employed forphosphate removal, particularly where a predetermined adjustment of pHis involved. However, from a practical matter the use, where possible,of the same material for both simplifies the preparation, enabling thepurchase of only the one material, in greater quantities, and possiblylower cost, and further, may involve less complex reactions.

The proportions, assuming the use of the same material for bothphosphate removal and floc formation, may be generally set forth asfollows: the coagulant will be initially present in an amount sufficientfor reaction with all of the reactionable phosphates present in suchwater, i.e. those capable of being precipitated out of solution. Inaddition, a further amount of coagulant is provided to supply sufficientfloc for the efficient removal of substantially all suspended andcolloidal material in the sewage, and where required, the alkalinematerial would initially be present in an amount sufficient to reactwith such further amount of coagulant adapted to provide a pre-reactedfloc. The agglomeration-promoting material should be present merely inan amount sufficient to insure the desired improved agglomeration.

The respective totals of each of such materials may be limited tosubstantially that providing reasonable excesses thereof consistent withinsuring the presence of adequate amounts thereof to accomplish therespective specified purposes as too much chemicals can produce adverseaffects, particularly among others with respect to pH and zetapotential.

The invention thus enables the practice of a very simple method ofchemically treating water, particularly that containing sewage wastes,in connection with the purification thereof, and in particular theremoval of phosphates and suspended and colloidal materials, in whichthe coagulant and any required alkaline reactive material are, ineffect, simultaneously introduced into the effluent, along with theagglomeration promoting material, with the proportions of the respectivematerials thus being sufficient to remove substantially all reactionablephosphates present in the water, together with the removal of allsuspended and colloidal material by means of the floc provided, and veryeffective and rapid agglomeration being achieved by the inclusion of theagglomeration-promoting material, following which the precipitated andagglomerated materials may thereafter be removed from the effluent, forexample, by settling, filtration and adsorption steps.

As previously mentioned, considerable work has heretofore been done inconnection with polyelectrolytes and it is believed that it isunnecessary to go into a detailed discussion with respect thereto.However, while it is possible that other polyelectrolytes may beemployed, we have found that excellent results can be achieved by theuse of a synthetic, high molecular weight (1 million and up) acrylamidecopolymer. Such polyacrylamide, which is essentially non-ionic insolution, has a formula, the general structure of which is as follows:##STR1## The polyacrylamide is essentially non-ionic in solutionsbecause of the preponderance of amide groups, although a small portionof the amide groups are usually hydrolyzed to anionic carboxylgroupings. As herein utilized, the polyacrylamide results in theformation of strong bonds when the colloidal floc is adsorbed on themixed bed of the tertiary adsorption filter.

The exact mechanism of such bridging action is unknown, but is suspectedto be a chemical reaction. It has been found to be particularlyeffective when operating with a zeta potential between -5 to -13, andwhen operation at 0 to -5 zeta potential the polyelectrolyte makes upfor deficiencies due to rapidly changing sewage conditions. Color bodieswould appear to be best adsorbed and filtered at 0 ZP with properlydesigned filter adsorption media such as herein provided. Liquid-solidadsorption techniques within the Gibbs theoretical approach(particularly those of high suspended solids content) is of greatestimportance in sewage treatment processes. The range of strongagglomeration, precipitation and filtration takes place at a zetapotential of +5. The zeta potential, and thus the colloid stability ofelectrostatic colloids is a function of the valence, type andconcentration thereof. Consequently, as the polyacrylamide is non-ionicit will not effect the zeta potential and will thus permit the same toremain at an effective value.

As previously mentioned, conceivably, dependent upon operatingconditions and the end results desired or tolerable, coagulants andreactive materials commonly employed, i.e. sodium aluminate, sulphatesof aluminum and iron, and ferric chloride may be employed, together witha suitable alkaline reactive material for those other than thealuminate, at least in accordance with some of the features of theinvention. Consequently as the aluminum compounds, i.e. sodium aluminateand aluminum sulphate appear to offer the greatest advantages over theothers, eliminating possible complications with respect to color in thefinal effluent and other problems with respect to pH control and zetapotential, as well as achieving relatively poor results particularlywith respect to excessive and intolerably increasing agglomeration timesrequired, and possibly complicating the chemical reactions, sodiumaluminate and aluminum sulphate present the least problems and providethe greatest universality of use, in view of which the others may inmost cases advantageously be dropped from consideration. In particularit would appear that the aluminum comounds are especially suitable, forsupplying the desired floc and thus it would appear that substitution ofthe other coagulants would preferably be limited to inclusion forphosphate precipitation. Again, in this connection, it should be kept inmind that the use of an iron salt may involve resoluble ionizationthrough anaerobic digestion, particularly ferrous sulphate, and it wouldappear that of this group ferric chloride probably is preferable.Likewise, if phosphate removal, color and long agglomeration times arenot of major importance, such coagulants might be employed, at least asa part of the supply of prereacted floc. It would, however, appeardesirable, if not necessary in most applications utilizing the type ofapparatus illustrated, for the achievement of the desired substantiallyinstantaneous flocculation and agglomeration, to employ at least apercentage of aluminum sulphate or sodium aluminate. Consequently, itwould appear to be the most simple and efficient solution to normallylimit use to either or both of these materials.

Again, consideration of the effect on the pH must be taken intoconsideration, to insure that the selected combination of materials willnot adversely affect the pH. While pH at least theoretically could becorrected by the addition of suitable correcting agents, obviously, inmost cases it will be preferable to employ a coagulant which will have abeneficial effect on the pH without the necessity of adding additionalmaterials solely for such correction.

In this connection, studies have been made with the common flocculentsand if necessary, cooperable alkaline reactive agents, to determine themost effective materials for use in the practice of the invention,specifically alum (Al₂)SO4)₃. 14H₂ O), sodium aluminate (Na₂ Al₂ O₄),ferrous sulphate (FeSO₄. 7H₂ O), ferric sulphate (Fe₂ (SO₄)₃), andferric chloride (FeCl₃)x. In addition, with the exception of sodiumaluminate, an alkaline reactive agent is normally employed with theothers, alum usually involving the use of calcium bicarbonate(Ca(HCO₃)₂), sodium carbonate (Na₂ CO₃) or calcium hydroxide (Ca(OH₂);calcium hydroxide with ferrous sulphate; and calcium bicarbonate orcalcium hydroxide with ferric sulfate or ferric chloride.

On the basis of such studies it is believed that the aluminum compoundsare preferable over the others for the following reason:

1. The aluminum ion is colorless and its compounds are usually white,whereas ferric and ferrous ions of yellow and green, respectively, formcolored compounds.

2. Aluminum presents no interference with biological nitrification orcarbon and solids removal.

3. Mixed sludge presents better settling charateristics in the mixedliquor than either biological sludge or aluminum hydroxide floc alone.

4. Aluminum phosphate precipitate retains its identity through anaerobicdigestion and is not resolubilized, i.e. reduced supernatant phosphorousrecycle, as phosphorous is not released fromm aluminum precipitateduriing anaerobic digestion.

5. Relative ease of handling and mixing of materials, as well asstability thereof.

6. Use of alum and alkaline agent, and/or sodium aluminate providessimple control of pH, eliminating use of additional materials therefor,and simultaneously provides the same metal ion.

7. Enables use of minimum number of material with greater quantity andless cost.

8. Iron compounds are most effective for phosphorous removal at theundesirable low pH of 4.5 to 5.0 for ferric compounds, and theundesirable high pH of 8 for ferrous compounds, while aluminum compoundsperform effectively closer to 7. The use of aluminum compounds thusenables effective control of pH and zeta potential without the use ofadditional materials, included solely to adjust the pH.

9. The aluminum compounds provide large surface area of thechemical-biological floc, for effective adsorption to the floc surfaceand coagulation of fine precipitated particles.

In view of the above, detailed discussion of chemical materials, and theamounts thereof in the practice of the present invention, will belimited to the two most preferable, aluminum sulphate and sodiumaluminate, and where aluminum sulphate is employed as the floc-formingcoagulant, sodium carbonate (soda ash) will be employed, illustratively,as the alkaline reactive agent (particularly for ease in handling).Likewise, amounts will be based on a plant having approximately 500gal./day capacity with non-industrial raw sewage having an approximateconstituent composition range as follows:

                  Table 1                                                         ______________________________________                                        Constituent            Concentration mg/1                                     ______________________________________                                        BOD.sub.5 - 20° C.                                                                            115-425                                                pH                     6.7-7.6                                                Suspended solids       165-895                                                Settleable solids ml/l/hr.                                                                           10-20                                                  Phosphorous as PO.sub.4                                                                              12-18                                                  ______________________________________                                    

Based upon such a system and sewage composition, utiliing aluminumsulphate and soda ash, with the total amounts being introduced into theeffluent in the manner previously described excellent results have beenobtained with the following proportions:

    ______________________________________                                        Aluminum sulfate     250 mg/l                                                 Soda ash             120 mg/l                                                 Polyelectrolyte       1 mg/l                                                  ______________________________________                                    

As previously mentioned, preferably a portion of the chemicals areintroduced into the primary-secondary chamber 21, preferably just beforethe initiation of the settling period with the remaining quantity beinginjected during the pump-down cycle.

Studies have indicated that for a system of this capacity with average,non-industrial sewage, the proportions of the chemical constituentswould normally range between the following dependent of course on thecharacter of the sewage:

    ______________________________________                                        Aluminum sulphate    200 mg/l to 350 mg/l                                     Soda ash              90 mg/l to 150 mg/l                                     Polyelectrolyte      0.5 mg/l to  10 mg/l                                     ______________________________________                                    

In the event that a low initial pH of the sewage is involved, it wouldnormally be desirable to employ sodium aluminate instead of the aluminumsulphate for at least a part of the latter, in which case the overallranges would be as follows, (keeping in mind that the proportions ofsulphate and aluminate would vary inversely and that the presence ofsoda ash would vary in accordance with the amount of sulphate utilizedfor floc formation):

    ______________________________________                                        Aluminum sulphate     0-350 mg/l                                              Soda ash              0-150 mg/l                                              Sodium aluminate     150- 0 mg/;                                              Polyacrylamide       0.5- 10 mg/l                                             ______________________________________                                    

Where no aluminum sulphate is employed, excellent results have beenobtained with effluent having a pH on the order of approximately 5.5with the following.

    ______________________________________                                        Sodium aluminate     100 mg/l                                                 Polyacrylamide        1 mg/l                                                  ______________________________________                                    

Where intermediate pH values are employed, various combinationsemploying both aluminum sulphate and sodium aluminate have provedeffective. FIG. 11 is a graph illustrating in line a the effect ofvarious combinations of the two coagulants, together with curve b forsodium aluminate alone. Superimposed on this graph is a line crepresenting the relative effect of aluminum sulphate, soda ash andpolyacrylamide, without sodium aluminate. The latter curve of course isnot plotted on the abscissa in parts of sodium aluminate, but rather,theoretically in parts of aluminum sulphate. It is intended to showmerely that with an initial pH between 6.5 and 7, the combination ofalum 250 mg/l, soda ash 120 mg/l and polyelectrolyte 1 mg/l, the pH israised to between 7 and 7.1.

The curve for the combination of both aluminum salts is reasonablyaccurate for ranges of alum between 25 to 150 mg/l, soda ash between 10to 75 mg/l, and polyelectrolyte of 1 mg/l.

No need is seen to include specific amounts when other alkaline reactiveagents are employed as, in general, equivalent mole amounts thereof maybe substituted for the sodium carbonate.

While the other coagulants are usable in varying degrees and undervarying conditions, their effectiveness, as compared with aluminumsalts, is such as to make it practical to rely on the latter. It wouldappear that the use of the other coagulants is primarily dependent uponspecial cases involving unusual combinations of pH and wastecontaminants, but where any of the disadvantages, previously discussed,are not critical, i.e. color, undesirable optimum pH, resolubility, longperiod for flocculation, etc., some of the advantages of the presentinvention may be derived by their use, provided the conditions are suchthat the desired pH and zeta potential controls are achieved when thecomponents are present in suitable quantities to provide adequate flocand phosphate precipitation. No figures can be given in this respect assubstantially every situation will have to be resolved on its own factsand conditions. It might be mentioned, however, that by proper selectionof materials, together with additions of aluminum coagulants, a suitablepH control, etc. may, in at least some cases, be effected. However, ifthis is necessary, it would appear much more advantageous to initiallyemploy the aluminum coagulants.

EXAMPLES OF CHEMICAL MATERIALS

As a basis for use of such materials the following examples are given,primarily on the basis of flocculation, without consideration of all thevariables previously discussed as to pH, zeta potential, phosphateremoval and resolubility, or possible disadvantages with respect tocolor, slow flocculation, etc. In general iron salts, when utilizedwithout additional aluminum salts, provide such slow flocculation thatfrom a practical standpoint consideration of their use in conjunctionwith the present type of system may be limited to a discussion ofcombinations with such aluminum salts.

All of the examples utilized a polyacrylamide and secondary effluent forthe test sewage, having the following composition:

    ______________________________________                                        (1) Total solids           1310 mg/l                                          (2) Settleable solids ml/l/hr.                                                                           Trace                                              (3) Suspended solids       12.0 mg/l                                          (4) pH value               6.4                                                (5) BOD.sub.5, 20° C.                                                                             15.                                                (6) Total Phosphate        20. mg/l                                           (7) Turbility J.T.U.       17.                                                (8) Alkalinity, Total as CaCO.sub.3 mg/l                                                                 10.                                                ______________________________________                                    

EXAMPLE 1

    ______________________________________                                        FeSO.sub.4 . 7H.sub.2 O                                                                            197.5 mg/l                                               Ca (OH).sub.2        52.5 mg/l                                                Na.sub.2 Al.sub.2 O.sub.4 . 3H.sub.2 O                                                             50.0 mg/l                                                Polyelectrolyte       1.0 mg/l                                                ______________________________________                                    

Results:

1. Relatively thin floc formed in first two minutes, thereafter startedto settle.

2. Orange colored precipitate.

3. Final pH 7.2-7.3

EXAMPLE 2

    ______________________________________                                        Fe.sub.2 (SO.sub.4).sub.3 . 2H.sub.2 O                                                              67 mg/l                                                 Ca(OA).sub.2          33.4 mg/l                                               Al.sub.2 (SO.sub.4).sub.3 . 14H.sub.2 O                                                             100. mg/l                                               Polyelectrolyte       1. mg/l                                                 ______________________________________                                    

Results:

1. Relatively thin floc formed in two minutes, thereafter started tosettle.

2. Orange-yellow colored precipitate.

3. Final pH--6.0-6.1

EXAMPLE 3

    ______________________________________                                        Fe.sub.2 (SO.sub.4).sub.3 . 2H.sub.2 O                                                              67 mg/l                                                 Ca(OH).sub.2          33.4 mg/l                                               Al.sub. 2 (SO.sub.4).sub.3 . 14H.sub.2 O                                                            100. mg/l                                               Polyelectrolyte       1. mg/l                                                 ______________________________________                                    

Results:

1. Relatively thin floc formed in two minutes, thereafter started tosettle.

2. Orange-yellow colored precipitate.

3. Final pH--6.0-6.1

EXAMPLE 4

    ______________________________________                                        FeCl.sub.3 . 6 H.sub.2 O                                                                          107 mg/l                                                  Ca(OH).sub.2        43 mg/l                                                   Polyelectrolyte      1 mg/l                                                   ______________________________________                                    

Results:

1. Relatively thin floc formed in two minutes, thereafter started tosettle.

2. Pale-yellow colored precipitate.

3. Final pH 5.9

EXAMPLE 5

    ______________________________________                                        FeCl.sub.3 . 6H.sub.2 O                                                                            107 mg/l                                                 Ca(OH).sub.2         43 mg/l                                                  Na.sub.2 Al.sub.2 O.sub.4 . 3H.sub.2 O                                                             50 mg/l                                                  Polyelectrolyte       1 mg/l                                                  ______________________________________                                    

Results:

1. Floc formed in one to two minutes, thereafter started to settle.

2. Pale-yellow colored floc.

3. Final pH 7.1

The following examples of various combinations of aluminum salts and/oralkaline reactive agents are presented for illustration and comparison,if desired, with the above examples.

EXAMPLE 6

    ______________________________________                                        Na.sub.2 Al.sub.2 O.sub.4 . 3H.sub.2 O                                                             100. mg/l                                                Polyelectrolyte       1. mg/l                                                 ______________________________________                                    

Results:

1. Floc formed in less than one minute, grew in size in next minute andthereafter started to settle.

2. No color.

3. Final pH 7.7.

EXAMPLE 7

    ______________________________________                                        Al.sub.2 (SO.sub.4).sub.3 . 14 H.sub.2 O                                                                 250. mg/l                                          Na(OH)                     100. mg/l                                          Polyelectrolyte             1. mg/l                                           ______________________________________                                    

Results:

1. Floc formed in one minute, started to settle in next minute.

2. No color.

3. Final pH 6.9-7.0

EXAMPLE 8

    ______________________________________                                        Na.sub.2 Al.sub.2 O.sub.3 . 3 H.sub.2 O                                                             50. mg/l                                                Al.sub.2 (SO.sub.4).sub.3 . 14 H.sub.2 O                                                            50. mg/l                                                ______________________________________                                    

Results:

1. Floc formed in one to two minutes, thereafter started to settle.

2. No color.

3. Final pH 6.6-6.7

EXAMPLE 9

    ______________________________________                                        Al.sub.2 (SO.sub.4).sub.3 . 14 H.sub.2 O                                                           250. mg/l                                                Ca(OH).sub.2         100. mg/l                                                Polyelectrolyte       1. mg/l                                                 ______________________________________                                    

Results:

1. Floc formed in one minute started settling in next minute.

2. Floc size and settling rate good.

3. No color.

4. Final pH 6.5-6.6

The following tabulated examples illustrate pH control utilizing variouscombinations of aluminum salts, employing the same sample effluent asthe previous examples but with pH previously adjusted to 5.5, andillustrate the control of pH with different proportions of such salts.

EXAMPLE 10

    ______________________________________                                                            Conc. mg/l                                                ______________________________________                                        Al.sub.2 (SO.sub.4)3 . 14 A.sub.2 O                                                                 25     50     100  150                                  Na.sub.2 CO.sub.3     10     25     50   75                                   Polyelectrolyte       1.0    1.0    1.0  1.0                                                      pH values                                                 ______________________________________                                        Final pH with        50 mg/l  6.5  6.5  6.5  6.5                              following additions of                                                                            100 mg/l  6.8  6.7  6.7  6.8                              Na.sub.2 Al.sub.2 O4 . 3H.sub.2 O                                                                 150 mg/l  7.3  7.3  7.3  7.3                              ______________________________________                                    

Cumulative Results:

1. Floc formed in first thirty seconds to one minute, grew in size andsettled in one to two minutes.

2. No color.

3. Most floc settled in three to five minutes.

While examples of iron sulphate omitting aluminum salts, have not beenillustrated, as their characteristics would normally permit useprimarily in extremely limited situations, it is believed that theexpert in the field would have no difficulty, in the light of thepresent teachings to resolve their use in such situations. However,calculated compositions should be confirmed by empirical studies, as iscommon practice in this field.

It might be mentioned that calcium hydroxide theoretically could beemployed as the flocculant. Combinations of 100-250 mg/l with 1 mg/lpolyelectrolyte have proved very efficient from the standpoint of flocformation, and when introduced into effluent samples as initially setforth, resulted in very rapid floc formation and settling action butwith a final pH of 8.2-8.5. However, as PO₄ removal is dependent on PHand lime requires an optimum pH of 9.5-11 for such removal, the use ofline normally would not be practical for phosphate removal, as it wouldin all probability be necessary to initially adjust the pH upward, forexample, by the addition of a large amount of lime, and thensubsequently reduce the pH by an acidic agent to a suitable value forultimate discharge.

PREPARATION OF CHEMICAL MATERIAL

As previously mentioned the chemical material, as used in the apparatusdescribed, is an aqueous mixture of one or more coagulants, an alkalinematerial, if necessary, and a polyelectrolyte. In preparing thematerial, assuming that the system involved has a 500 gallon per daycapacity, and the material is to supply 250 mg/l of alum, 120 mg/l sodaash and 1 mg/l polyelectrolyte, such quantities of material may bereadily prepared, for example, to provide three liters of liquidmaterial, whereby the supply to the effluent being treated would be at aproportional rate of 6 cc per gallon of effluent. To provide this ratiothe three liters would contain 1.9 grams of polyelectrolyte, 1.05 poundsof alum and 0.455 pounds of soda ash.

The material may be readily prepared by taking two volumes of water thetotal of which is less than three liters and introducing the alum in onevolume and the soda ash in the other, with the two solutions thusprepared being mixed together with an accompanying formation of floc.The polyelectrolyte is then introduced thereto and additional wateradded to bring the total to three liters. 6 cc of such material wouldthen provide the desired amounts of alum, soda ash and polyelectrolyteper liter of effluent. The amount of water employed in the preparationof the material is not critical and preferably is kept as low aspractical, consistent with bringing the respective constituents intosolution, effect formation of the desired floc and enable suitablefeeding. At the same time, it will be appreciated that as the chemicalsare preferably supplied to the system in quantities to last a reasonablylong period of time for example 30 to 60 days or more, it is advisableto keep the total amount of material to be stored at a minimum.

As the material contains prereacted floc, to insure feeding of uniformquantities thereof, the storage tank CS therefor preferably is providedwith agitation means, as heretofore described, (comprising electricmotor CS1 adapted to rotate the agitating blades CS2) to make sure thatthe injected volumes contain uniform quantities of components.

It has been found that a material having the proportions specified, andof such volume, provides an adequate aqueous vehicle for the floc andother components, the quantities to be fed being sufficiently large thatreasonably accurate control thereof may be effected and at the same timepreferably involve the use of less than one gallon of material per day.At the same time, the material is free flowing with a minimum tendencyto clog the feed pumps or supply lines therefor. As the cost of thechemical materials is relatively inexpensive and comparatively smallquantities are employed, the cost of the materials per gallon ofeffluent is well within practical values.

Likewise, where combinations of aluminate and sulphate are involved,they can, if desirable, be readily independently prepared and thensuitably mixed together.

In accordance with another feature of the invention the chemicalmaterials conveniently may be suitably processed in dry form and adaptedto be combined with water just prior to use.

In this case, the respective materials are the form of dry discreteparticles which may be placed in the desired proportions, in a suitablegrinding apparatus, for example a ball or micro mill, and ground to asuitable particle size. That particularly suitable is one that will passthrough a 325 U.S. standard screen, i.e. on the order of 40 microns.While the material may be individually ground and thereafter mixed,grinding of the mixture has the advantage of a combined operation.

The dry mixture so formed may be packaged, transported and handled insuch form, and suitably mixed with water, at time of use, to provide thedesired concentration.

Again, the use of sodium aluminate, aluminum sulphate and sodiumcarbonate would appear to offer the greatest advantage as to ease ofhandling, etc. in dry form as compared with other more highly corrosiveor caustic materials.

OPERATIONAL PARAMETERS

A system constructed in accordance with the present invention presentsrelatively small physical dimensions, considering the results achieved,as compared with systems employing numerous tanks etc. and at the sametime achieving poorer results. In a 500 gal/day capacity the overallarea of the installation may be only 4'×8', with the primary-secondarychamber 21 having a height of 4.5' and the vertical column 14' having anarea of 4' by 4.3' and a height or depth of 3'. Overall dimensions thuswould be 4' wide, 8' long and 7.5' high. For comparison, a system havinga 3125 gal/day capacity and capable of handling 50 persons would havecorresponding overall dimensions of only 6' in width, 9' in height, and14' in length, and a 12,500 gal/day capacity for at least 200 personswould have corresponding overall dimensions of 71/2×11'×28'. Obviously,in some cases it may be practical to install a plurality of units ratherthan one large unit.

In view of the fact, previously discussed, with respect to widelyvarying factors in the operation of this type of system, it is believedpreferable to more or less limit specific parameters to the operation ofthe specific system illustrated, under average home conditions asdistinguished from industrial conditions, from which one skilled in theart should have little difficulty in applying the teachings hereof toother conditions and applications. It is believed apparent, aspreviously mentioned with respect to the chemical materials,calculations and situations such as this cannot be resolved withmathematical precision and in many if not most cases mathematicalconcepts should be confirmed with empirical studies.

Suitable operational parameters (other than composition) of chemicalmaterials, therefore will be discussed in connection with the systemheretofore described, having an approximate operating capacity of 500gals. per cycle of operation, i.e. for example 24-hour cycle, in whichcase the primary-secondary tank 20 could have an approximate volume of800-850 gals. with approximately 200-225 gals. residual being maintainedin the tank at all times, i.e. normal total maximum contentapproximately 700-725 gals.

The blower B, in such case preferably should provide at least 18-25 CFat a head of 35"-40" of water. Calculations with respect thereto can bereadily derived in accordance with present techniques and teachings withrespect to aeration procedures, and conveniently, air may be supplied at40 cubic feet per minute under such pressure, to provide a wide marginof safety and insure maximum aeration.

In the embodiment of the invention illustrated, again assuming that theprimary-secondary tank has a capacity of 800-850 gals., the tertiaryunit may be constructed, for example, with a bed area of 3 feet andadopted to contain a minimum of substantially 12 cubic feet of filterand adsorption materials in which embodiment five layers L₁ to L₅, withthe layer L₁ comprising a 1" layer of red flint which would run fromapproximately 5/8" to 3/8" in size. Layer L₂ may comprise a 1" layer ofred flint which would run from 1/2" to 1/4" in size. Layer 3 maycomprise 11/2" layer of quartz 1.5 to 0.9 mm effective size (uniformitycoefficient 1.75). Layer 4 may comprise a 21/2" layer of quartz 0.5 to0.3 mm effective size (U.C. 1.45).

The remaining layer L₅ may comprise a hydraulic mix of activated carbonand quartz with the particle sizes of carbon ranging from 1/11" to 1/4"(4×10) mixed with #5 quartz with a uniformity coefficient of 1.45, and aheight of approximately 3 to 4 ft.

The grid 35, with specific materials, such as that described, may be soconstructed that the grid openings have minimum dimensions of fromapproximately 1/2" to 3/4", while the perforate portion 38' of thetrough may be the equivalent of #16 mesh. It might be mentioned thatwhile the carbon of the tertiary unit may contain some particles smallenough to pass through the perforate portion into the primary-secondarychamber, this will do no harm as the fine carbon will provide extendedsurface therein, as has more or less recently become known, therebyimproving performance.

The extended surface area of the fine carbon provides a bacterialbreeding surface of large area, facilitating oxidation and thusimproving efficiency of aeration. It may even be desirable in at leastsome cases to actually seed the primary-secondary with fine carbon.

It will be appreciated that with increase in the capacity of the systemthe capacity of the teritary structure will also be correspondinglyincreased. This may be accomplished by increasing the area of thetertiary beds, increasing the height of the beds or a combination ofboth. In the first case the flow per unit of area may remain the same,and in the second the flow rate may be suitably increased. In any eventthe flow should be maintained at a rate that will insure that thelayered structure of the beds is operatively maintained, i.e. thelayered formation is not disrupted and with no liquid break-through.

Following the aeration cycle and settling cycle of from about 2.5 to 3hours, the settled effluent is pumped through the tertiary column bymeans of the pump P1. With such physical parameters it has been foundthat very effective results can be achieved with a secondary effluentflow rate of between 2 and 3 gal/min./ft.² of bed area. Simultaneouslywith the flow in the tertiary structure, the chemical materials areinjected into the secondary effluent line prior to entering thetertiary, and on the basis of a chemical mixture employing alum, sodaash and polyacrylamide with proportions, for example, being such as toprovide 250 mg/l, 120 mg/l of soda ash and 1 mg/l of polyacrylamide, theacqueous mixture employed may, for example, have a concentration ofmaterials such that 6 cc per gallon of secondary effluent will providethe desired mg/l concentration.

It has been found that best results are obtained when a portion of thedesired amount of chemicals are added to the effluent in theprimary-secondary tank 20, preferably prior to the settling operation,with the remainder being injected into the secondary effluent lineduring the pump-down cycle. Very advantageous results can be achieved byutilization of half of the desired quantity, i.e. 3 cc of chemicals pergal. in the primary-secondary tank, with the remaining 3 cc beinginjected in the secondary effluent line. As previously mentioned, thepumps P2 and P3 preferably are so constructed and operated that therequisite amounts of chemicals will be supplied at the desired times.

Studies, made with introduction of the chemicals taking place entirelyin the primary-secondary tank, or all introduction taking place byinjection into the secondary effluent line during pump-down, indicatedthat desired optimum results could not be achieved solely with either.In the case of supply solely to the tank, it was found that there was atendency for the chemically treated settled secondary effluent to stillcontain some suspended solids and colloidal particles which requiredfurther chemical treatment. Likewise, as substantially instantagglomeration and flocculation must take place in the secondary effluentline, i.e. between the injection of the chemicals into the line andentry in the tertiary tank 22, optimum agglomeration of all of theprereact floc supply to the effluent normally would not take place insuch short span of time. However, when the chemicals were divided,efficient agglomeration took place in the primary-secondary tank, and atthe same time additional chemical injection into the tertiary line,resulted in a very efficient removal of any remaining suspended solidsand colloidal particles, as the latter were readily picked up in thesecond stage agglomeration and effectively removed in the bottom portionof the tertiary structure which functions as a filtration media (as wellas a support for the adsorption bed). Any remaining colloidal particlesand dissolved organic solids were subsequently removed by adsorption onthe surface of the activated carbon of the tertiary structure. It willbe appreciated that the effluent flow through the tertiary unit can bereadily controlled by means of the flow control valves FV1 and FV2,which may be suitably adjustable or, where the system is designed for aspecific application, may be permanently set valves adapted to providethe desired flow rate. The use of two flow control valves enables aflexibility and accuracy in the control.

While operating parameters with respect to regeneration of the tertiaryunit may be varied, in dependence upon other design and operatingparameters, it has been found that exceptionally efficient regenerationof the tertiary unit can be accomplished by the use of air at a pressureof from 10-30 psi with a flow rate of approximately 5-15 CFM inconnection with the employment of water. In the system heretoforedescribed, preferably such water is heated to 160°-170° to insuremaximum effectiveness.

We have found that excellent results can be achieved by employing threesteps, the first solely with air, the second a combination of air andhot water, and the third a flushing with water only. While obviouslyduration of each operation is subject to variation, particularly anextension of the duration thereof, it has been found that the followinginsures achievement of the desired results, providing adequate excessesof air and water and at the same time not unduly prolonging theoperations. In the recommended procedure, the storage tank 61 may have anormal storage capacity of approximately 90 gals.

In a preferred regeneration cycle, air is passed through the tertiaryunit at the specified volume and pressure for three minutes, andthereafter continued for another twelve minutes during which period hotwater is simultaneously supplied at a flow rate of 5 gals. per minute(utilizing 60 gals.) and terminated with a flushing operation, utilizingonly water, for a duration of 4 minutes (utilizing 20 gals.) whereby theregeneration cycle utilizes a total of 80 gals. of water.

In determining the parameters for the regeneration cycle it will beappreciated that the volume and pressure of the regenerating air (orgas) should be sufficient to adequately expand the filtration andadsorption beds to insure effective oxidation and flushing of allparticles with hot water during the combined air-water operation at thesame time without undesirably changing size distribution of theparticles comprising the respective beds, i.e. disturb the operationalarrangement and function of the respective layers of filtration andadsorption materials. Likewise, the amount of air (or gas) and wateremployed must be sufficient to insure adequate oxidation and flushing ofthe tertiary materials into the primary-secondary tank. The final 4minutes of flushing insures that the water remaining in the tertiaryunit at the end of the regenerating cycle will have the same purity asthat therein prior to the preceding pump-down cycle. In this connectionit should be kept in mind that as the tertiary unit is, to a largeextent, filled with the filtration and adsorption materials, the netvolume available for the retention of water is relatively low and isthus substantially fully supplied by the final flushing cycle.

RESULTS ACHIEVED BY THE PRESENT INVENTION

The following table represents actual results obtained in the operationof a 500-gal. treatment unit constructed and operated in accordance withthe invention, and utilizing the methods and materials heretoforedescribed. The chemical treatment in this particular case employedaluminum sulphate, proportioned in accordance with the teachings of theinvention. The table is a comparison between raw sewage, secondaryeffluent before and after chemical treatment and the nature of theeffluent discharged from the tertiary unit

                                      Table 2                                     __________________________________________________________________________                 Conc. in mg/l                                                                                  Tertiary                                                          Secondary Effluent                                                                        Effluent                                                          Before                                                                              After                                                              Raw  Chemical                                                                            Chemical    Average                                   Constituent  Sewage                                                                             Treatment                                                                           Treatment                                                                           Low                                                                              High                                                                             Test                                      __________________________________________________________________________    BOD.sub.5 20° C.                                                                    115-425                                                                            15-50 10-25 1.0                                                                              0.3                                                                              1.4                                       pH           6.7-7.6                                                                            6.3-7.7                                                                             6.5-7.5                                                                             6.9                                                                              7.1                                                                              7.0                                       D.O. at 20° C.                                                                      --   4-7   4-7   5. 7.5                                                                              6.7                                       S.Solids     165-895                                                                            5-136 8-20  0  2.0                                                                              0.6                                       Settleable solids, mg/l/hr                                                                 10-20                                                                              trace trace 0  0  0                                         Phosphorous as PO.sub.4                                                                    12-18                                                                              8-13  6-10  0.3                                                                              4.0                                                                               1.57                                     Nitrate as N --   --    --    10 15 --                                        Turbidity, JTU    10-40 8-30  0.95                                                                              5  2.15                                     __________________________________________________________________________

The results of operation for a period of over six months of a systemembodying the invention may be set forth in a greater detail withrespect to the character of the effluent discharged from the tertiaryunit in the following table, in which the results are set forth in theform of the largest and smallest value ascertained, together with theaverage value (and the number of samplings on which the results werebased).

                                      Table 3                                     __________________________________________________________________________                          Tertiary Effluent                                                             L     H   A  No. Tests                                  __________________________________________________________________________      Temp. °C. at 9:00 A.M.                                                                     10°                                                                          21°                                                                        14.8°                                                                     50                                           pH                  6.9   7.1 7.0                                                                              49                                           D.O. at 20° C., mg/l                                                                       5.0   7.5 6.7                                                                              47                                           BOD.sub.5 20° C., mg/l                                                                     1.0   3.0 1.4                                                                              27                                           Settleable solids, ml/l/hr                                                                        0     0   0  50                                           Suspended solids, mg/l                                                                            0     2   0.6                                                                              42                                           Phosphate as PO.sub.4, mg/l                                                                       0.3   4.0 1.57                                                                             17                                           Phosphate as P, mg/l                                                                              0.1   1.3 0.51                                                                             17                                           Nitrate as N, mg/l  10    15. 11.8                                                                             11                                         10.                                                                             Nitrate as NO.sub.3, mg/l                                                                         44    66  52 11                                           Nitrite as N, mg/l  0.17         1                                            Odor                      None                                                Turbidity, JTU      0.95  5   2.15                                                                             47                                           Color units         80    130 104                                                                              7                                            Total alkalinity as CaCo.sub.3, ppm                                                               28    80  40 7                                            Phenolphthalein alkalinity as CaCo.sub.3 ppm                                                      0     0   0  7                                            Total hardness as CaCo.sub.3, ppm                                                                 510          (1)                                          Calcium hardness as CaCo.sub.3, ppm                                                               290                                                       Magnesium hardness as CaCo.sub.3, ppm                                                             220          (1)                                        20.                                                                             Coliform bacteria, MPN/100 ml                                                                     0                                                         (Chlorinated effluent samples,                                                1 ppm residual cl.sub.2)                                                      Flow rate thru Tertiary Column                                                                    2 gpm/ft..sup.2                                         __________________________________________________________________________

It will be appreciated from the above results that the effluent from thesystem is of high quality and readily usable for a wide variety ofpurposes. Conceivably, with the addition of chlorination, a potablewater supply may be derived. Likewise, the renovated water, preferablywith the addition of a chlorine residual, is readily usable for a lawnand garden sprinkling, larger scale irrigation, home sanitation andwashing operations, swimming pools, and industrial processes.

Based on an average home, or family of five persons, the cost of thechemicals for the tertiary treatment would run about two cents perperson per day and with larger units the per capita cost would bereduced. Obviously, where the water is reused, a saving in water costswould materially reduce the overall cost of operation.

It will also be appreciated that in this single very compact sewagetreatment plant, employing only two basic containers or tanks, ascompared with the multiple installations commonly employed, the presentsystem fully meets the goals and standards which have been establishedfor compliance on or after 12-31-77, established by the U.S.Environmental Pollution Agency for treated discharge effluents whichcurrently are as follows:

TABLE 4 POLLUTION STANDARDS

A. Deoxygenating Wastes

1. On and after 7/1/72, no effluent shall exceed 30 mg/l of BOD₅ or 37mg/l of suspended solids.

2. On and after 7/1/72, no effluent from any source whose untreatedwaste load is 10,000 population equivalents or more, or from any sourcedischarging into the Chicago River System or into the Calumet RiverSystem, shall exceed 20 mg/l BOD₅ or 25 mg/l of suspended solids.

3. On or after 12/31/73, no effluent whose dilution ratio is less thanfive to one shall exceed 10 mg/l of BOD₅ or 12 mg/l of suspended solids.

4. On or after 12/31/74, no effluent discharged to the Lake MichiganBasin shall exceed 4 mg/l BOD₅ or 5 mg/l of suspended solids.

5. On or after 12/31/77, no effluent from any source whose untreatedwaste load is 500,000 population equivalents or more shall exceed 4 mg/lof BOD₅ or 5 mg/l of suspended solids.

B. Other Standards

1. Bacteria--no effluent may exceed 400 fecal coliform per 100 ml after7/31/72.

2. pH--shall lie within the range of 6.5 to 9.0 except for naturalcauses.

3. Dissolved oxygen--shall not be less than 6.0 mg/l during at least 16hours of any 24 hours period, nor less than 5.0 mg/l at any time.

While the accumulation of sludge heretofore has presented a problem insewage systems of the general type here involved, operation of a pilotplant, embodying the invention, over an extended period of time hasindicated that with the reflex operations involved, and the extensiveaeration provided, together with anaerobic digestion in any such sludge,the latter is apparently limited to inorganic and organic matter noteffectively combining with oxygen or resolved into gases, andconstitutes a relatively small amount. It would appear, at the presenttime, that a system embodying the invention, conceivably, might run forat least a period of years without cleaning, possibly 5 years or more.

As previously mentioned the system can be employed anywhere where poweris available for the various operation, and obviously is not limitedsolely to commercial electrical power supplies.

It will further be appreciated that the cycling operations considerablyreduce the required sizes of the various units, particularly thetertiary unit, the construction of which, for practical purposes,completely eliminates relatively frequent replacement or regeneration ofthe carbon by removal from the unit, as is customary with manyinstallations.

While the present disclosure has not touched upon safety devices whichmight be incorporated in the equipment, it is believed apparent thatvarious monitoring devices may be employed which would give an alarm inthe event the normal cycle of operation is disturbed or ceases. Forexample, circuits may be readily provided wherein an alarm will be givenin the event a pump-down flow or regeneration flow fails to take placewithin the normal cycle of operation, or if a mal-function takes placewith any of the other valves, pump, blower or compressor.

Having thus described our invention it will be apparent that althoughvarious minor modifications might be suggested by those versed in theart, it should be understood that we wish to embody within the scope ofthe patent granted hereon all such modifications as reasonably, andproperly come within the scope of our contribution to the art.

We claim as our invention:
 1. A chemical material, for use in thepurification treatment of water, particularly for the automatictreatment of sewage and the like containing phosphates, suspended andcolloidal materials, and adapted to be mixed with a quantity of water toform a liquid concentrate containing reacted floc, which quantity issmall in volume as compared with the quantity of water to be treated,with such concentrate and prereacted floc therein being adapted to beintroduced in quantities, small as compared with said concentratevolume, into such water to be treated, comprising a water-solublecoagulant, a reactive agent therefor, additional coagulant over thatreactive with such agent, and a water-soluble agglomeration-promotingmaterial, with the proportions of the respective materials being suchthat, upon introduction of such concentrate in suitable quantity intothe water to be treated, the respective amounts of coagulant andreactive agent will provide an adequate amount of prereacted flocsufficient for the removal of substantially all suspended and colloidalmaterial present in such water, the amount of said additional coagulantwill be sufficient for reaction with all of the reactionable phosphatespresent in such water, and the amount of agglomeration-promotingmaterial will be sufficient to promote agglomeration in such water, therespective total amounts of prereacted floc, coagulant, andagglomeration-promoting material being sufficient to provide reasonableexcesses thereof consistent with insuring adequate amounts of therespective materials for the specified purposes, and insufficient tomaterially, undesirably affect the pH of such water, and/or the zetapotential from a range of -5 to +5.
 2. A chemical material according toclaim 1, wherein said prereacted floc is derived from a coagulantselected from the group comprising sodium aluminate, and aluminumsulphate, ferric and ferrous sulphate, and ferric chloride, reacted withan alkaline reactive agent selected from a group comprising sodiumcarbonate, sodium hydroxide, calcium hydroxide, and calcium bicarbonate.3. A chemical material according to claim 2, wherein said prereactedfloc is derived from a coagulant selected from the group comprisingsodium aluminate; and aluminum sulphate reacted with an alkalinereactive agent selected from a group comprising calcium hydroxide,sodium hydroxide, sodium carbonate and calcium bicarbonate, and saidagglomeration-promoting material is an organic non-ionic polyacrilamide.4. A material according to claim 2, wherein said additional coagulant isselected from the group comprising sodium aluminate, aluminum sulphate,ferric and ferrous sulphates and ferric chloride.
 5. A materialaccording to claim 2 wherein the coagulant forming the excess is soselected, in dependence upon the acidity of the waste waters in whichthe material is to be utilized, that the reactive products therefrom inphosphate removal, in the presence of relatively high initial acidity,tend to relatively greatly increase the pH of the water, or in thepresence of relatively low initial acidity, tends to affect a relativelylesser increase in the pH of the water.
 6. A material according to claim5, wherein said excess coagulant, for use with relatively high acidity,comprises sodium aluminate.
 7. A material according to claim 5, whereinsaid excess coagulant, for use with relatively low acidity, comprisesaluminum sulphate.
 8. A material according to claim 5, wherein saidchemicals comprise an aqueous mixture of aluminum sulphate, sodiumcarbonate, sodium aluminate and an organic high molecular weightpolyelectrolyte, in amounts to provide approximate amounts per liter ofeffluent as follows:

    ______________________________________                                        aluminum sulphate    25-150 mg/l                                              sodium carbonate     10-75 mg/l                                               sodium aluminate     150-50 mg/l                                              polyelectrolyte      0.5-10 mg/l.                                             ______________________________________                                    


9. A material according to claim 2, wherein said chemical materialcomprises an aqueous mixture of aluminum sulphate, sodium carbonate andan organic high molecular weight polyelectrolyte in amounts to provideapproximate amounts per liter of effluent as follows:

    ______________________________________                                        aluminum sulphate    200-350 mg/l                                             sodium carbonate     90-150 mg/l                                              polyelectrolyte      .5-10 mg/l.                                              ______________________________________                                    


10. A material according to claim 9, wherein the proportions of theconstituents of said mixture are in amounts to provide:

    ______________________________________                                        aluminum sulphate    250 mg/l                                                 sodium carbonate     120 mg/l                                                 polyelectrolyte      1 mg/l.                                                  ______________________________________                                    


11. A material according to claim 10, wherein the polyelectrolyte isnon-ionic polyacrylamide.
 12. A material according to claim 1, whereinsaid material comprises an aqueous mixture of the components thereof.13. A material according to claim 1, wherein said material is in theform of dry intermixed discrete particles of a size adapted to be addedto water, at time of use, to readily form an aqueous mixture.
 14. Amaterial according to claim 13, wherein said particles are of a size topass through a 325 U.S. standard screen.